Method and apparatus for processing uplink data by DRX-mode terminal in mobile telecommunication system

ABSTRACT

Disclosed is a method and apparatus for transmitting uplink data by a terminal performing a DRX operation in a mobile telecommunication system. According to the method and apparatus, when a UE transmits the uplink data, the UE variably controls given active and sleep periods in consideration of whether or not retransmission for the uplink data is performed, thereby more flexibly operating in the DRX mode.

PRIORITY

This application is a Continuation application of U.S. application Ser.No. 11/972,722 filed in the U.S. Patent and Trademark Office on Jan. 11,2008, which claims priority to an application entitled “Method andApparatus for Processing Uplink Data by DRX-Mode Terminal in MobileTelecommunication System” filed in the Korean Industrial Property Officeon Jan. 15, 2007 and Aug. 8, 2007, and assigned Serial Nos. 2007-0004232and 2007-0079598, respectively, the contents of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile telecommunication system, andmore particularly to a method and apparatus for processing uplink databy a terminal performing a discontinuous reception (DRX) mode operationin a mobile telecommunication system.

2. Description of the Related Art

The universal mobile telecommunication service (UMTS) system is a 3^(rd)generation asynchronous mobile telecommunication system which is basedon European mobile telecommunication systems, that is, GSM (GlobalSystem for Mobile Communications) and GPRS (General Packet RadioServices), and uses a CDMA (Code Division Multiple Access) scheme.

As a way to reduce terminal power consumption, the conventional 3^(rd)generation mobile telecommunication system employs a discontinuousreception (DRX) mode in which a terminal transitions to an idle statewhen it has no data to transmit/receive, and discontinuously receives apaging message in the idle state. In other words, the terminal wakes up,that is, powers on its transceiver, at a predefined time, and monitors apaging channel. If the terminal receives a paging message over thepaging channel, it transitions to a connection state. However, if theterminal receives no paging message, it powers off its transceiver, andmaintains a sleep state until the next wakeup time.

The reason why the DRX mode is applied to a conventional idle-modeterminal is that the conventional mobile telecommunication systemcenters on a voice call, and thus the terminal stays in a connectionstate only for a relatively short time.

However, an evolved mobile telecommunication system, such as LTE (LongTerm Evolution) that is currently under discussion, is expected toprovide a terminal with a packet service, as well as the voice call. Theterminal that is provided with the packet service may stay in aconnection state for a relatively long time, and a problem to be solvedin the evolved mobile telecommunication system is to minimize the powerconsumption of the terminal that may stay in a connection state for sucha long time.

In the evolve mobile telecommunication system, therefore, a network mayappropriately set up the DRX mode in consideration of thecharacteristics of services supported to a terminal that is in aconnection state.

FIG. 1 illustrates the concept of a DRX operation.

Referring to FIG. 1, the DRX operation generally included the followingelements:

-   -   Active State (or Active Period): A period during which a        receiver of a terminal is turned on. In the active state, the        terminal checks if there is downlink data, and receives data        when the downlink data exists.    -   Sleep State (or Sleep Period): A period during which a receiver        of a terminal is turned off. It is established for the        minimization of terminal power consumption.    -   DRX Cycle Length 110, 120: A length between an active period and        the next active period.

Since the DRX operation as mentioned above is aimed at receiving datawhile minimizing terminal power consumption, the beginning and end of anactive state is defined in connection with data reception. That is, thebeginning point of an active state, the end point of an active state,etc. are determined by considering a data reception time, the amount ofreceived data, and so forth.

In addition, uplink data may occur in a terminal that is in theabove-mentioned DRX operation. A description will be given of how theDRX operation is affected by the uplink data occurring in a terminalthat is in the DRX operation, with reference to FIG. 2.

Referring to FIG. 2, reference numeral “a” shows that a terminalperforms a DRX operation consisting of active states 205, 210, 215 and217 and sleep states.

Reference numeral “b” shows that when the terminal should perform atransmission operation according to the occurrence of uplink data in theterminal performing the DRX operation (as designated by referencenumeral “220”), it must transition to an active state and perform thetransmission operation 225 although it is in a sleep state of the DRXoperation at a corresponding time.

Also, in response to the transmission operation 225, the transmissionoperation may be accompanied with an operation of transmitting anACKnowledgement (ACK)/Non-ACKnowledgement (NACK) signal according to aHybrid Automatic Repeat Request (HARQ).

When the HARQ operation is performed, the terminal maintains an activestate so as to receive from a base station the ACK/NACK signal, whichindicates whether or not the reception of the uplink data is erroneous.

Consequently, a period during which the terminal actually stays in anactive state can be defined by the summation of active state periods ofthe DRX operation and an active state period for the transmissionoperation, as represented by reference numeral “c”.

For example, it is assumed that active state periods 205, 210, 215 and217 for downlink data reception are established for any terminal, anduplink data occurs at a certain time “e” belonging to a sleep stateperiod, according to which the terminal transitions to an active state(as designated by reference numeral “225”), and then maintains theactive state until a time “f”.

Thus, the actual overall active state period of the terminal correspondsto the summation of the active state periods for data reception and theactive state period for data transmission 230, 235, 240 and 245.

With regard to this, in order to ensure the efficiency of the DRXoperation when the terminal transitions to the active state for datatransmission, as described above, it is very important to define whenthe terminal ends the active state.

In the conventional mobile telecommunication system, such as the UMTSsystem, once a terminal transitions to an active state for uplink datatransmission, the terminal maintains the active state until the receiptof a separate instruction from the network. That is, the terminal endsthe active state and resumes the DRX operation under the control of thenetwork.

In addition, the DRX operation in the conventional UMTS system targetsan idle-mode terminal that is not accompanied by substantial datatransmission/reception.

However, in the evolved mobile telecommunication system that is newlydiscussed based the UMTS system, a connection-mode terminal performs aDRX operation in correspondence to the packet service. This DRXoperation is quite different from that of an idle-mode terminalaccompanied by no data transmission/reception.

SUMMARY OF THE INVENTION

In the context of the above description, that is, in view of theminimization of power consumption, it is not desirable to keep aconnection-mode terminal in an active state when uplink data occurs inthe connection-mode terminal that performs the DRX operation.

Therefore, when a connection-mode terminal performs a discontinuoustransmission/reception operation in the evolve mobile telecommunicationsystem, it is necessary to newly define an active state according touplink data occurrence. That is, in the evolved mobile telecommunicationsystem, there is an urgent need to propose a way for a terminal to moreefficiently consume power by defining an active state according toterminal modes and performing the discontinuous transmission/receptionoperation of the terminal, corresponding to the defined active state.

Accordingly, the present invention has been made to solve at least theabove-mentioned problems occurring in the prior art, and the presentinvention provides a method and an apparatus for transmitting uplinkdata and supporting a DRX operation in a mobile telecommunicationsystem.

Further, the present invention provides a method and apparatus forefficiently controlling terminal power consumption by allowing aconnection-mode terminal to variably establish an active state accordingto uplink data occurrence in a mobile telecommunication system.

Further, the present invention provides a method and apparatus forinforming a network of uplink data transmission and sleep stateresumption by a connection-mode terminal in a mobile telecommunicationsystem.

In accordance with another aspect of the present invention, there isprovided a method of transmitting uplink data by a terminal performing aDRX operation in a mobile telecommunication system, the method includesas the uplink data occurs, suspending the DRX operation, andtransmitting the uplink data; informing a base station of whether or notthe last data of the uplink data is transmitted; setting a different DRXcycle length according to whether or not the transmitted last data leadsto downlink data reception; and resuming the DRX operation correspondingto the differently set DRX cycle length.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and advantages of the presentinvention will be more apparent from the following detailed descriptiontaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram explaining the concept of a DRX operation;

FIG. 2 is a diagram illustrating how a DRX operation is affected byuplink data that occurs in a terminal performing the DRX operation;

FIG. 3 is a diagram illustrating the overall DRX operation of a terminalthat processes uplink data in accordance with an exemplary embodiment ofthe present invention;

FIG. 4 is a block diagram illustrating a terminal apparatus inaccordance with an exemplary embodiment of the present invention;

FIG. 5 is a diagram illustrating signaling flows and processingoperations of F-a terminal and a base station in accordance with anexemplary embodiment of the present invention;

FIG. 6 is a flowchart illustrating an operation of an RLC block of aterminal apparatus in accordance with an exemplary embodiment of thepresent invention;

FIG. 7 is a flowchart illustrating operations of an MAC block and a DRXcontroller block of a terminal apparatus in accordance with an exemplaryembodiment of the present invention;

FIG. 8 is a diagram illustrating a structure of an MAC PDU in accordancewith an exemplary embodiment of the present invention;

FIG. 9 is a flowchart illustrating an operation of a terminal inaccordance with a second exemplary embodiment of the present invention;

FIG. 10 is a flowchart illustrating an operation of a terminal inaccordance with a third exemplary embodiment of the present invention;

FIG. 11 is a flowchart illustrating an operation of a terminal inaccordance with a fourth exemplary embodiment of the present invention;and

FIG. 12 is a flowchart illustrating an operation of a terminal inaccordance with a fifth exemplary embodiment of the present invention

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

Hereinafter, exemplary embodiments of the present invention will bedescribed with reference to the accompanying drawings. In the followingdescription, a detailed description of known functions andconfigurations incorporated herein will be omitted when it may make thesubject matter of the present invention rather unclear. Further, variousspecific definitions found in the following description are providedonly to help general understanding of the present invention, and it isapparent to those skilled in the art that the present invention can beimplemented without such definitions.

By way of example, the present invention will be described in connectionwith the LTE system that is newly proposed as an evolved mobiletelecommunication system based on the 3^(rd) generation asynchronousmobile telecommunication system. The present invention to be describedbelow may be applied to other mobile telecommunication systems employinga DRX operation. Also, the present invention may be applied to mobiletelecommunication systems employing base station signaling.

In addition, the present invention may also be applied to mobiletelecommunication systems supporting uplink services. Moreover, thepresent invention may also be applied to mobile telecommunicationsystems employing Automatic Repeat Request (ARQ) and Hybrid ARQ (HARQ).

The present invention provides a method and apparatus for suspending adiscontinuous reception (DRX) operation when uplink data occurs in aterminal that is in the DRX operation, transmitting the uplink data,resuming at the most appropriate time according to the characteristic ofthe transmitted data, and then informing a network of the resumption ofthe DRX operation.

More specially, in the present invention, a terminal performing a DRXoperation transitions to an active state so as to transmit uplink data,transmits the uplink data, and then appropriately sets the end point ofthe active state according to the characteristic of the transmitteduplink data. Also, the terminal informs a base station of the set endpoint of the active state.

FIG. 3 illustrates the overall operation of a User Equipment (UE) thatcontrols a DRX operation according to an exemplary embodiment of thepresent invention.

In the following description, the fact that the UE transitions to anactive state means that the UE turns on its transceiver. Also, the factthat the UE ends an active state means that the UE turns off itstransceiver. Since the UE does not substantially perform the DRXoperation when it is in an active state, the fact that the UE ends theactive state has the same meaning as the fact that the UE resumes theDRX operation.

In the present invention, uplink data may be classified into two types,that is, uplink data that leads to downlink data reception, and uplinkdata that does not lead to downlink data reception.

As an example, the uplink data that leads to downlink data reception maybe the last packet of data to which an ARQ of two layers is applied, andthe uplink data that does not lead to downlink data reception may bedata to which an ARQ is not applied. Here, the ARQ is a technique inwhich a receiving side checks the serial numbers of the receivedpackets, and requests a transmitting side to retransmit packets that arenot received.

With regard to this, in a typical ARQ protocol, such as Radio LinkControl (RLC), a transmitting side transmits a series of packets, thelast packet of which includes control information requesting a receivingside to report the reception status of the packets.

Such control information is referred to as a “POLL”. On receiving apacket including the POLL, the receiving side transmits a receptionstatus report message that includes the serial numbers of receivedpackets and the serial numbers of packets required to be retransmitted.

If a UE transmits a packet including the POLL, the UE preferablymaintains an active state because a reception status report message willbe transmitted sooner or later from the UE.

Contrarily, if a UE receives the POLL, and transmits a reception statusreport message, the UE preferably ends an active state and resumes a DRXoperation because packets are not transmitted/received any longer afterthe reception status report message is transmitted.

a. Embodiment 1

In a first embodiment of the present invention, when a UE transmits thelast packet stored in a transmission buffer, the UE includes controlinformation for informing an evolved Node B (ENB) of the end of anactive state and the resumption of a DRX operation in an Media AccessControl Packet Data Unit (MAC PDU) containing the last packet accordingto the type of the packet. When the UE completes transmitting the MACPDU, the UE resumes the DRX operation.

According to the type of the packet, the UE transmits an MAC PDU thatdoes not include control information for informing the ENB of the end ofan active state and the resumption of a DRX operation, drives a timerwhen the transmission of the MAC PDU is completed, and maintains theactive state until the timer expires. Since a UE determines whether ornot to end an active state in this way, the UE can end the active stateat the most appropriate time. Also, since the UE informs an ENB of theend of the active state, the ENB can prevent transmission resources frombeing allocated to UEs that are in a sleep state.

Referring to FIG. 3, if uplink data occurs in a UE performing a DRXoperation, as designated by reference numeral “305”, the UE reports abuffer status to an ENB, thereby requesting the ENB to allocate atransmission resource thereto, as designated by reference numeral “310”.Also, the UE starts an active period during which it operates in anactive state, as designated by reference numeral “315”. The fact thatthe UE starts the active period has the same meaning as the fact thatthe UE suspends the DRX operation.

The UE monitors a downlink control channel. If the transmission resourceis allocated to the UE, the UE transmits the uplink data by using theallocated transmission resource. That is, if the UE is allocated thetransmission resource, the UE transmits the uplink data over theallocated transmission resource.

At a point of time when the UE transmits the last data stored in atransmission buffer, if the last data satisfies one of the following twoDRX RESUME triggering conditions, the UE includes control informationfor informing the ENB of DRX operation resumption in an MAC PDUcontaining the last data, and transmits the MAC PDU with the controlinformation included therein, as designated by reference numeral “345”,and then resumes the DRX operation when the transmission of the MAC PDUis completed, as designated by reference numeral “350”. That is, the UEends the active period, and transitions to a sleep state.

The following are DRX RESUME triggering conditions:

[1] In the case where the transmission buffers of all other logicalchannels are empty, and the last data to be transmitted is stored in thetransmission buffer of a logical channel to which ARQ is not applied.

[2] In the case where a reception status report message not includingretransmission request information, that is, a reception status reportmessage including only an ACK signal, is transmitted with the last data,and data including POLL information is not transmitted before thetransmission of the last data or a reception status report message hasbeen already received in response to data including POLL information,even if the data including POLL information has been transmitted.

If the last data stored in the transmission buffer satisfies neither ofthe DRX RESUME triggering conditions when the UE transmits the lastdata, the UE completes transmitting an MAC PDU containing the last data,as designated by reference numeral “320”, and drives a timer T for atime “t”, as designated by reference numeral “325”.

If downlink data is not received until the timer T expires, the UE endsthe active period, and transitions to a sleep state, as designated byreference numeral “335”.

However, if downlink data is received before the timer T expires, the UEmaintains the active period until the ENB instructs the UE to end theactive period or data is received for another given period of time.

As mentioned above, in this embodiment, a UE informs a network ofwhether or not to resume a DRX operation when transmitting the lastuplink data, and then maintains an active state or operates in a sleepstate according to the DRX operation.

FIG. 4 illustrates a UE apparatus controlling a DRX operation accordingto an exemplary embodiment of the present invention.

Referring to FIG. 4, the UE apparatus includes a transceiver block 435,an MAC block 425, RLC blocks 405, 410, and 415, an RRC block 420, and aDRX controller block 430.

Each of the RLC blocks 405, 410, and 415 is created for each service,and functions to reconstruct a packet occurring in an upper layer into asize suitable for transmission over a radio frequency (RF) channel andto apply ARQ to the packet, if necessary.

Data transferred from any one of the RLC blocks 405, 410, or 415 to theMAC block 425 or data transferred from the MAC block 425 to any one ofthe RLC blocks 405, 410, or 415 is called a radio link control packetdata unit (RLC PDU).

The MAC block 425 multiplexes packets configured in the RLC blocks 405,410, and 415 into an MAC PDU and transmits the MAC PDU through thetransceiver block 435, or demultiplexes RLC PDUs from an MAC PDUreceived through the transceiver block 435 and transfers the RLC PDUs tothe corresponding RLC blocks 405, 410, and 415.

The transceiver block 435 transmits/receives generated uplink data overa physical channel.

The DRX controller block 430 controls a DRX operation according to DRXsetup. That is, the DRX controller block 430 turns on the transceiverblock 435 during an active period, and turns off the transceiver block435 during a sleep period.

In other words, the DRX controller block 430 follows instructions of theRRL block 420, or controls the transceiver block 435 according to thecharacteristic of data generated in each of the RLC blocks 405, 410, and415.

That is, when an RLC PDU transmitted in a specific RLC block is the lastdata to which ARQ is not applied, the DRX controller block 430 turns offthe transceiver block 435. The DRX controller block 430 also turns offthe transceiver block 435 in the case of a reception status reportmessage not including retransmission request information.

The RRC block 420 controls the setup and release of various blocksrelated to wireless communication, including the RLC blocks 405, 410,and 415, the MAC block 425, the transceiver block 435, the DRXcontroller block 430, etc.

FIG. 5 illustrates signal flows between an ENB and a UE that variablymaintain a DRX operation according to an exemplary embodiment of thepresent invention.

Referring to FIG. 5, in step 515, the UE 505 receives a SETUP messagefrom the ENB (or an apparatus responsible for RF resource control in anetwork) 510.

The SETUP message configuration information of logical channels forproviding the UE with desired services, for example, information relatedto various timers or variables used in RLC blocks. If the UE performs aDRX operation, the SETUP message also includes DRX setup information.For example, the SETUP message includes information on a DRX cyclelength and its beginning point. Values of timer 1 and timer 2 are alsoincluded in the SETUP message.

According to setup information included in the SETUP message, an RLCblock of the UE 505 transfers the logical timer values and the DRX setupinformation to a DRX controller block, sets up logical channels based onthe configuration information according to logical channels, andtransitions to a connection mode. That is, in the present invention, anetwork and a connection-mode UE for which logical channels are set upperform a DRX operation.

On completing the SETUP step, in step 520, the UE and the ENB performthe DRX operation according to the DRX setup information. In otherwords, the UE wakes up at a wakeup time set between the UE and the ENB,that is, transitions to an active state, and determines if data isreceived.

If data is not received for a certain time in the active state or theENB instructs the UE to end the active period, the UE ends the activeperiod and transitions to a sleep state again.

If downlink data to be transmitted to the UE arrives at the ENB, the ENBstores the downlink data until the active period of the closest UEreaches. When the active period starts, the ENB transmits the storeddownlink data to the UE, and upon completing the transmission of thedownlink data, instructs the UE to end the active period. The UE thentransitions to a sleep state.

In step 525, the UE that is in the sleep state detects the occurrence ofuplink data to be transmitted to the ENB over a logical channel.

In step 530, the UE reports a buffer status to a scheduler of the ENB soas to transmit the uplink data. That is, the UE requests the ENB toallocate a transmission resource for transmitting the uplink data, andtransitions to an active state. In response to the buffer status report,the UE is allocated a transmission resource from the ENB over a downlinkcontrol channel, and transmits the uplink data over the allocatedtransmission resource.

In step 535, the UE that is transmitting the uplink data checks, priorto the transmission of the last data, if the last data satisfies any ofthe aforementioned DRX RESUME triggering conditions. That is, the UEchecks if the last uplink data is the last data in the transmissionbuffer of a logical channel to which ARQ is not applied or if the lastuplink data corresponds to a reception status report message notincluding retransmission request information.

When a result of the check in step 535 shows that the last uplink datasatisfies any of the DRX RESUME triggering conditions, in step 540, theUE includes control information called DRX RESUME in an MAC PDUcontaining the last data, and transmits the MAC PDU with the DRX RESUMEcontrol information included therein. That is, in step 540, uponcompleting transmitting the MAC PDU, the UE ends the active period, andtransitions to a sleep state. In other words, the UE resumes the DRXoperation.

If a result of the check in step 535 shows that the last uplink datasatisfies neither of the DRX RESUME triggering conditions, in step 545,the UE completes transmitting the MAC PDU containing the last data, andthen drives timer 1. If downlink data is not received from the ENB untilthe timer 1 expires, the UE ends the active period, and transitions to asleep state again.

Contrarily, if downlink data is received from the ENB before the timer 1expires, the UE maintains the active period until any one of the DRXRESUME triggering conditions is satisfied.

The following are Conditions for ending an active state:

-   -   After the latest data is received, data is not received during        timer 2.    -   The ENB instructs the UE to end the active period.

Here, the timer 1 is a timer that is driven for a time during which theUE can maintain power consumption to the full extent of its power,thereby maintaining an active state, and the timer 2 is a timer that isdriven for a time set for maintaining an active state after downlinkdata is received from the ENB. The timers 1 and 2 are set to values atwhich a system operator can maintain optimal terminal power. Althoughthe timers 1 and 2 are set to different values, the ENB and the UE mayaccord their DRX points with each other again by ending the active stateat the same point of time.

Corresponding to such an operation of the UE, the ENB receives a bufferstatus report from the UE performing a DRX operation to therebyrecognize that the UE suspends the DRX operation and maintains an activestate. Also, the ENB allocates an appropriate transmission resource tothe UE, as determined by a scheduler, and receives an MAC PDU containingDRX RESUME to thereby recognize that the UE resumes the DRX operation.

Even if the MAC PDU containing DRX RESUME is not received from the UE,the DRX operation is resumed when data is not received from the UE andthere is no data to be transmitted to the UE for a given period of time.

The ENB may clearly instruct the UE to resume the DRX operation bytransmitting to the UE an MAC PDU, which contains control informationfor informing the UE of the resumption of the DRX operation, and mayalso make the UE itself resume the DRX operation by transmitting no datato the UE for a certain period of time.

FIG. 6 illustrates the operation of the RLC block that variably controlsan active state in the UE apparatus according to an exemplary embodimentof the present invention.

Referring to FIG. 6, in step 605, a scheduling layer inside of the UEinstructs the RLC block to transfer data to the MAC block.

The RLC block proceeds to step 610, and determines if the transferreddata is the last data stored in the transmission buffer. When the datais the last data, the RLC block proceeds to step 615, and otherwise,proceeds to step 630.

In step 630, the RLC block reconstructs the data stored in thetransmission buffer into an RLC PDU with a size required by thescheduler, transfers the reconstructed RLC PDU to the MAC layer, andthen waits for the next instruction from the scheduler.

Upon ascertaining that the data is the last data, in step 615, the RLCblock checks if an ARQ procedure is performed for the data. If a resultof the check in step 615 shows that the data is not subjected to the ARQprocedure, that is, an RLC Unacknowledged Mode (UM) is operated, the RLCblock proceeds to step 625.

Contrarily, if a result of the check in step 615 shows that the data issubjected to the ARQ procedure, the RLC block proceeds to step 620.

In step 620, the RLC block checks if the last data satisfies thefollowing indicator 1 triggering conditions.

The following are indicator 1 triggering conditions:

-   -   Status report message including retransmission request.    -   There is no POLL in response to which a response is not        received. That is, any RLC PDU containing POLL has not been        previously transmitted or a reception status report message in        response to an RLC PDU containing POLL has been already        received, even if the RLC PDU has been transmitted.

If a result of the check in step 620 shows that the last data satisfiesall the indicator 1 triggering conditions, the RLC block proceeds tostep 625. However, if the last data does not satisfy any one of theindicator 1 triggering conditions, the RLC block proceeds to step 635.

In step 625, the RLC block configures the last data into an RLC PDU, andtransfers the RLC PDU together with indicator 1 to a lower layer. Theindicator 1 indicates that the RLC PDU transferred therewith is the lastdata satisfying the DRX RESUME triggering condition. That is, ARO is notperformed for the last data, which corresponds to data that does notlead to downlink data reception. Thus, the UE transmits the last datatogether with the DRX RESUME, and resumes the DRX operation when thetransmission of the last data is completed.

Contrarily, in step 635, the RLC block configures the last data into anRLC PDU, and transfers the RLC PDU together with indicator 2 to a lowerlayer. The indicator 2 indicates that the RLC PDU transferred therewithis the last data that does not satisfy the DRX RESUME triggeringcondition. This corresponds to a situation where downlink data receptionis considered necessary during a set timer. Thus, upon completing thetransmission of the last data, the UE determines a time for DRXoperation resumption by driving a given timer.

FIG. 7 illustrates the operations of the MAC block and the DRXcontroller block of the UE apparatus according to an exemplaryembodiment of the present invention.

Referring to FIG. 7, in step 705, uplink data occurs in any logicalchannel transmission buffer of the UE to which a DRX operation isapplied.

In step 710, the MAC block requests a scheduler of an ENB to allocate atransmission resource thereto. With regard to this, the MAC blockreports the buffer status for the data occurring in the transmissionbuffer to the ENB, thereby requests the scheduler of the ENB to allocatea transmission resource necessary for transmitting the data. Also, instep 715, the DRX controller block controls the transceiver block tostart an active period.

When the transmission resource is allocated to the UE in step 720, instep 725, a scheduler of the MAC block instructs the RLC block toconfigure an RLC PDU with a size transmittable over the allocatedtransmission resource, and transfer the configured RLC PDU to the MACblock.

When the RLC PDU reaches the MAC block in step 730, in step 735, the DRCcontroller block checks if indicator 1 is transferred together with theRLC PDU.

In other words, the DRX controller block checks if the RLC PDU is thelast data and is a reception status report message not including aretransmission request or RLC UM data.

If a result of the check in step 735 shows that the indicator 1 istransferred together, the DRX controller block proceeds to step 740, andotherwise, proceeds to step 750.

In step 740, the DRX controller block controls the MAC block to includecontrol information, DRX RESUME, in an MAC PDU containing the RLC PDU,and transmit the MAC PDU with the control information included therein.The DRX RESUME control information may be implemented as a type of MACcontrol information. For example, referring to FIG. 8, an indicator 810indicating existence/non-existence of the RESUME control information isincluded in an MAC header. If the DRX RESUME needs to be transmitted,the indicator 810 is set to an appropriate value, and the DRX RESUME 820may be included in the rear portion of the MAC PDU.

Upon receiving the DRX RESUME control information, the ENB recognizesthat the relevant UE resumes the DRX operation, and thus does notallocate a transmission resource or transmits data to the UE until thenext active period.

In step 745, the DRX controller block ends the active period when thetransmission of the MAC PDU is completed, and controls the transceiverblock to enter a sleep period. In other words, the DRX operation isresumed.

In step 750, the DRC controller block checks if the RLC PDU istransferred together with indicator 2. The fact that the indicator 2 istransferred together means that the DRX operation must not be resumedimmediately because the RLC PDU is the last data, but data may bereceived from the ENB after the RLC PDU is transmitted. Consequently,the DRX controller block proceeds to step 755 when the indicator 2 istransferred together, and proceeds to step 720 when the indicator 2 isnot transferred together because this means that data to be transmittedstill remains in the RLC transmission buffer.

In step 755, the MAC block transmits the MAC PDU, and the DRC controllerblock drives timer 1 and proceeds to step 760 when the transmission ofthe MAC PDU is completed.

In step 760, the DRX controller block determines if downlink data isreceived before the timer 1 expires. If a result of the determination instep 760 shows that downlink data is not received before the timer 1expires, the DRX controller block proceeds to step 765, and ends theactive period and resumes the DRX operation.

Contrarily, if a result of the determination in step 760 shows thatdownlink data is received before the timer 1 expires, the DRX controllerblock proceeds to step 770, and maintains the active period until thecondition for ending the active period is satisfied. If the conditionfor ending the active period is satisfied, then the DRX controller blockresumes the DRX operation.

FIG. 8 illustrates the structure of an MAC PDU according to an exemplaryembodiment of the present invention.

Referring to FIG. 8, the MAC block configures the MAC PDU by includingan MAC header 805 together with control information called DRX RESUME820 in an RLC PDU transferred from the RLC block. With regard to this,the MAC PDU may further include an indicator 810 indicating whether ornot the DRX RESUME control information 820 exists. That is, on one hand,the indicator 810 that is set to 1 indicates that the RLC PDUcorresponds to information for triggering the DRX RESUME according tothe present invention, and on the other hand, the indicator 810 that isset to 2 indicates that an active state is maintained for a time definedby a timer, and then the DRX RESUME is triggered.

b. Embodiment 2

In a second embodiment of the present invention, there is provided amethod for a UE performing a DRX operation to resume the DRX operationwhile adjusting the DRX cycle length thereof according to thecharacteristic of the last uplink data when resuming the DRX operationthat has been temporarily suspended for the transmission of uplink data.

FIG. 9 illustrates the operation of a UE according to the secondembodiment of the present invention.

Referring to FIG. 9, in step 905, uplink data occurs in any logicalchannel transmission buffer of the UE to which the DRX operation isapplied.

In step 910, the UE requests a scheduler of an ENB to allocate atransmission resource for reporting the status of the transmissionbuffer. More specially, the UE reports a buffer status for the dataoccurring in the transmission buffer to the ENB through the followingthree steps, thereby requesting the scheduler of the ENB to allocate atransmission resource necessary for transmitting the data.

A procedure of requesting transmission resource allocation may beperformed in the following three steps. Once the UE begins theprocedure, that is, the UE transmits a transmission resource allocationsignal to the ENB over a given physical channel, it suspends the DRXoperation immediately, and starts an active period.

The steps are as follows:

1. The UE requests the ENB to allocate a transmission resource for abuffer status report over a given physical channel.

2. The ENB allocates the transmission resource for a buffer statusreport to the UE.

3. The UE report a buffer status to the ENB by using the allocatedtransmission resource.

Once the UE begins on the procedure of requesting transmission resourceallocation, as mentioned above, the UE transmits a transmission resourceallocation signal to the ENB over a given physical channel, in step 915,the UE suspends the DRX operation immediately, and starts an activeperiod.

Upon suspending the DRX operation, the UE monitors a downlink controlchannel, and transmits the uplink data when the transmission resource isallocated to the UE over the downlink control channel.

The UE repeatedly performs an operation of transmitting the uplink databy using the allocated transmission resource until the transmission ofthe last data is completed.

In step 920, if the transmission of the last data is completed, and theUE determines that the ENB recognizes the transmitted data to be thelast data, the UE proceeds to step 925.

Although not illustrated in the drawing, when there is no more data tobe transmitted, the UE transmits the uplink data while addingmeaningless data, that is, padding, thereto. Thus, in transmitting thelast data, the UE inserts padding into the last data when the quantityof the allocated transmission resource is greater than the last data,thereby indirectly informing the ENB that there is no more data to betransmitted.

When the UE can add padding to the last data to thereby inform the ENBthat the transmission buffer is empty, the UE proceeds to step 925immediately after transmitting the last data.

Contrarily, if the quantity of the allocated transmission resourceexactly accords with the last data, the UE cannot inform the ENB thatthere is no more data to be transmitted, and there is a high possibilitythat the ENB allocates a transmission resource to the UE later on.Therefore, although the UE transmits the last data, it does not proceedto step 925, but maintains the active period if it does not insertpadding or information indicative of the last data into the last data.That is, the UE does not proceed to step 925 before it is allocated atransmission resource later on to thereby transmit information on thenon-existence of transmitted data to the ENB.

In step 925, the UE determines the characteristic of the last data,thereby deciding which DRX cycle length is applied to the DRX operation.

When the last data is data occurring in a logical channel to which ARQis not applied, or when the last data is data occurring in a logicalchannel to which ARQ is applied, but corresponds to a reception statusreport message not including retransmission request information, the UEproceeds to step 935, and otherwise, proceeds to step 930.

In step 930, the UE resumes the DRX operation, and applies a predefinedfirst DRX cycle length as the DRX cycle length of the resumed DRXoperation. In step 935, the UE resumes the DRX operation, and applies apredefined second DRX cycle length as the DRX cycle length of theresumed DRX operation.

The ENB signals the first and second DRX cycle lengths to the UE duringa call setup procedure, and the first DRX cycle length has a value lessthan that of the second DRX cycle length.

c. Embodiment 3

In a third embodiment of the present invention, there is a method andapparatus for determining whether a UE resumes a DRX operationimmediately after transmitting the last data or resumes the DX operationafter waiting for a given period of time according to the type of alogical channel to which the last data transmitted by the UE belongs.

FIG. 10 illustrates the operation of a UE according to the thirdembodiment of the present invention.

Before the UE performs the operation illustrated in FIG. 10, the UEtogether with an ENB determines according to logical channels whether ornot to drive a timer after transmitting the last data or informationindicating that there is no more data to be transmitted, and recognizestimer values to be applied according to logical channels. Thisinformation is indicated to the UE and the ENB through a call setupprocedure, etc. For example, a logical channel to which ARQ is appliedmay be set in such a manner as to drive the timer, and a logical channelto which ARQ is not applied may be set in such a manner as not to drivethe timer.

Referring to FIG. 10, in step 1005, uplink data occurs in any logicalchannel transmission buffer of the UE performing the DRX operation.

In step 1010, the UE requests a scheduler of the ENB to allocate atransmission resource thereto. Subsequently, in step 1015, the UE drivesits receiver unit, and then monitors if a transmission resource isallocated to the UE over a downlink control channel. If the UE isallocated an uplink transmission resource, in step 1020, the UE beginson uplink transmission over the allocated transmission resource, andcontinues the uplink transmission until no more data remains in thetransmission buffer. In step 1025, the UE transmits informationindicating that there is no more data to be transmitted, aftersuccessfully transmitting the last data or while transmitting the lastdata. Upon completing the transmission of the information indicatingthat there is no more data to be transmitted, the UE proceeds to step1030, and checks if the logical channel is a logical channel that is setin such a manner as to drive a timer after the transmission of theinformation indicating that there is no more data to be transmitted.

If a result of the check in step 1030 shows that the logical channel isnot a logical channel requiring driving the timer, in step 1035, the UEends the active period that has been started for the transmission of theuplink data, and resumes the DRX operation. That is, the UE continuesthe active period when the corresponding point of time falls within anactive period on the existing DRX operation, and turns off its receiverunit and waits until the next active period reaches when thecorresponding point of time does not fall within an active period on theexisting DRX operation.

However, if a result of the check in step 1030 shows that the logicalchannel is a logical channel requiring driving the timer, in step 1040,the UE drives the timer. Subsequently, the UE proceeds to step 1045, andchecks if there is data transmitted thereto until the timer expires.

If a result of the check in step 1045 shows that data is not receiveduntil the timer expires, the UE proceeds to step 1035, and ends theactive period and returns to the previous DRX operation. However, if aresult of the check in step 1045 shows that data is received to the UEbefore the timer expires, the UE proceeds to step 1050, and maintainsthe active period until the condition for ending the active period issatisfied. When the condition for ending the active period is satisfied,the UE ends the active period, and resumes the DRX operation.

d. Embodiment 4

In a fourth embodiment of the present invention, there is provided amethod and apparatus for resuming a DRX operation after a UE transmitsthe last data or information indicating that there is no more data to betransmitted, on condition that the DRX cycle length of the DRX operationto be resumed is determined according to the type of a logical channelto which the last data belongs.

FIG. 11 illustrates the operation of a UE according to the fourthembodiment of the present invention.

Before the UE performs the operation illustrated in FIG. 11, the UEtogether with an ENB recognizes a DRX cycle length to be applied to aDRX operation that is resumed after transmitting the last data orinformation indicating that there is no more data to be transmitted.This information is indicated to the UE and the ENB through a call setupprocedure, etc. For example, a first DRX cycle length corresponding to ashorter DRX cycle length may be set for a logical channel to which ARQis applied, and a second DRX cycle length corresponding to a longer DRXcycle length may be set for a logical channel to which ARQ is notapplied.

Referring to FIG. 11, in step 1105, uplink data occurs in any logicalchannel transmission buffer of the UE performing the DRX operation.

In step 1110, the UE requests a scheduler of the ENB to allocate atransmission resource thereto. Subsequently, in step 1115, the UE turnson its receiver unit, and then monitors if a transmission resource isallocated to the UE over a downlink control channel. If the UE isallocated an uplink transmission resource, in step 1120, the UE beginson uplink transmission over the allocated transmission resource, andcontinues the uplink transmission until no more data remains in thetransmission buffer. In step 1125, the UE transmits informationindicating that there is no more data to be transmitted, aftersuccessfully transmitting the last data or while transmitting the lastdata. Upon completing the transmission of the information indicatingthat there is no more data to be transmitted, in step 1130, the UEchecks if the DRX cycle length set for the logical channel to which thelast data belongs is the first DRX cycle length or the second DRX cyclelength. In step 1135, the UE ends the active period that has beenstarted for the transmission of the uplink data, and resumes the DRXoperation by using the first or second DRX cycle length.

c. Embodiment 5

In a fifth embodiment of the present invention, there is provided a wayto drive a timer for controlling DRX operation resumption at a timepoint when a UE is allocated a transmission resource over which totransmit information indicating that there is no more data to betransmitted, rather than at a point in time when the transmission of theinformation indicating that there is no more data to be transmitted iscompleted. This embodiment has an advantage of making a downlink DRXoperation as similar as possible to an uplink DRX operation.

FIG. 12 illustrates the operation of a UE according to the fifthembodiment of the present invention.

Referring to FIG. 12, in step 1205, uplink data occurs in any logicalchannel transmission buffer of the UE performing the DRX operation.

In step 1210, the UE requests a scheduler of an ENB to allocate atransmission resource thereto, and in step 1215, turns on its receiverunit. In step 1217, the UE monitors a Physical Downlink Common ControlCHannel (PDCCH). That is, the UE receives time/frequency resourcesmapped to the PDCCH, and performs UE-specific Cyclic Redundancy Check(CRC). If a result of the UE-specific CRC shows no error, this resultmeans that control information to be delivered to the UE, for example,information on downlink transmission resource allocation or uplinktransmission resource allocation, is included in the PDCCH. Contrarily,if a result of the UE-specific CRC shows any error, this result meansthat control information to be delivered to the UE is not included thePDCCH.

In step 1220, if the UE succeeds in decoding the PDCCH, in other words,if the UE receives the PDCCH that has no error in the UE-specific CRC,the UE proceeds to step 1225, and drives a given timer. The UE checks ifa new PDCCH is successfully decoded until the timer expires. If a newPDCCH is not successfully decoded until the timer expires, that is, ifthe UE is not allocated a downlink or uplink transmission resource againuntil the timer expires, the UE proceeds to step 1235 so as to determineif it is necessary to resume the DRX operation. Contrarily, if a newPDCCH is successfully decoded before the timer expires, the UE returnsto step 1225, and drives the timer again.

In step 1235, if the transmission buffer is empty, the UE checks if ithas already started transmitting an MAC PDU that includes informationindicating no more data to be transmitted. When the UE startstransmitting the MAC PDU including the last data and the informationindicating no more data to be transmitted, it sets an Empty Flag to“TRUE”. In step 1235, if the Empty Flag is set to “TRUE”, the UEproceeds to step 1240. However, if the Empty Flag is set to “FALSE”,that is, if data still remains in the transmission buffer of the UE orthe UE does not yet start transmitting the information indicating nomore data to be transmitted, the UE returns to step 1215, and continuesto monitor the PDCCH. The fact that the UE proceeds to step 1240 meansthat no data remains in the transmission buffer of the UE, and thetransmission of the information indicating no more data to betransmitted has been already completed or is in progress. Thus, in step1240, the UE checks if there is data that is under uplink HARQretransmission. If there is no data is under uplink HARQ retransmission,the UE immediately resumes the DRX operation. Contrarily, if there isdata that is under uplink HARQ retransmission, the UE completes the HARQretransmission, that is, performs retransmission until an HARQ ACK isreceived or the given maximum number of times of retransmission reaches,and then resumes the DRX operation.

According to the present invention as described above, when a UEtransmits uplink data, the UE variably controls given active and sleepperiods in consideration of whether or not retransmission for the uplinkdata is performed, thereby allowing a DRX operation to be more flexiblyused.

Further, the power consumption of a UE can be minimized by maintainingan active period to a variable length corresponding to thecharacteristic of uplink transmission data.

Further, since a UE informs a network of its active and sleep statescorresponding to a DRX mode, it is possible to for the network to ensurethe reliability and efficiency of transmission resource allocationaccording to uplink data transmission/reception.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

What is claimed is:
 1. A method of transmitting uplink data in a mobiletelecommunication system, the method comprising the steps of:transmitting, if the uplink data becomes available for transmission, ascheduling request for requesting uplink resources for the uplink dataand transitioning to an active state; monitoring a control channel inthe active state; transmitting the uplink data if the uplink resourcesare allocated; maintaining the active state during a first period afterthe uplink resources are allocated; and maintaining the active stateduring a second period to receive an acknowledge message correspondingto the uplink data.
 2. The method of claim 1, further comprising: endingthe active state if the second period has elapsed or a command forending the active state is received.
 3. An apparatus for transmittinguplink data in a mobile telecommunication system, the method comprising:a transceiver configured to transmit a scheduling request for requestinguplink resources for the uplink data if the uplink data becomesavailable for transmission, monitor control channel in an active state,and transmit the uplink data if the uplink resources are allocated; anda controller configured to transition to the active state after sendingthe scheduling request, maintain the active state during a first periodafter the uplink resources are allocated, and maintain the active stateduring a second period to receive an acknowledge message correspondingto the uplink data.
 4. The apparatus of claim 3, wherein the controllerends the active state if the second period has elapsed or a command forending the active state is received.